LERMA UMR8112

Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères



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Interstellar Medium and Plasmas

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What processes drive the evolution of interstellar matter in the Milky Way and in other galaxies ? What roles do the turbulence, the magnetic field, the cosmic rays, and the radiation field play in this evolution ? Those fundamental questions for modern Astrophysics now appear at many spatial scales and for a great variety of environments : from the galactic scales where the diffuse gas collapse to form the precursors of new stars ; down to the scale of proto-planetary disks where the central star strongly interacts with the surrounding matter ; and even in the stars themselves where the transport mechanisms are still unknown. To study all these astronomical objects, the group « Interstellar Medium and Plasmas » of the LERMA combine theoretical works, numerical modeling, 3D simulations, and observations of interstellar environments at high spectral and angular resolutions.

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On the observational side, our group is specialized in the treatment and the analysis of the data obtained with the most advanced space and ground-based observatories. Our expertise is particularly strong in the infrared and sub-millimeter domains which reveal the emission of atoms, molecules and interstellar dust. We have therefore been deeply involved in the recent successes and findings of Herschel and Planck space observatories, which we now follow up by collecting data with the new generation of instruments (in particular, APEX, ALMA, and soon NOEMA).

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On the numerical side, the codes developed in our group are internationally renowned as state-of-the-art tools for the analysis of interstellar matter and the interpretation of observational data. Our expertise extends from the conception of 3D numerical simulations of magnetohydrodynamics, which we run using high-level computational capacities (e.g. PRACE, MesoPSL), to the development of advanced numerical models. The strength of those models, which we provide to the community through the ISM and jets platform, is to solve a great number of microphysical processes at play in the interstellar medium, with prescriptions based on the results of laboratory experiments and theoretical studies which are partly performed in our laboratory.


Select one of the following links to know more about our activities


1. Turbulence & magnetic field

2. Matter / photon interactions

3. Stellar plasmas and laboratory astrophysics

4. Prestellar cores

5. Protostars, debris & jets

6. Accretion & ejection in stars


Click here to access our publications

Séminaires à venir

Vendredi 16 novembre 2018, 14h00
Salle de l'atelier, Paris
Quantum walks and astrophysical plasmas
Fabrice DEBBASCH
UPMC, LERMA, Paris
résumé :
Quantum walks (QWs) have been first considered by Feynman in the 1940's and later introduced systematically in the 1990's in the context of quantum information. These discrete automata are a universal quantum computation tool and their first experimental realisation is less than 10 years old (2009).

I will present some of the research conducted at the LERMA since 2012. I will explain that QWs can be viewed as models of Dirac fermions (electrons etc.) interacting with gauge fields like EM fields and gravitation and that QWs can be used to build self-consistent many body theories. These results pave the way towards new numerical simulations and laboratory experiments modelling astrophysical and cosmological relativistic quantum plasmas through QWs.
 
Vendredi 30 novembre 2018, 14h00
Salle de l'atelier, Paris
Multiscale star-formation in the Ophiuchus Molecular Cloud: from molecular clouds to brown-dwarfs formation
Bilal LADJELATE
IRAM
résumé :
From molecular clouds to stars, every step of the evolution of young stars can be observed in the submillimetric range. The Herschel Space Telescope observed, as part of the Herschel Gould Belt Survey, many molecular clouds. When these molecular clouds are fragmenting, dense prestellar cores accumulating dust and gas are forming and contracting. We performed a census of prestellar dense cores in the Ophiuchus Molecular Cloud, which appear to be coupled with filamentary structures, as part of the paradigm of star-formation inside interstellar filaments. The region was not previously known as filamentary, despite the observation of protostellar alignments. This molecular cloud is under the heavy feedback of active stars nearby seen in the structure of the molecular cloud. Oph B-11, detected with interferometric observations, is a brown dwarf precursor, which final mass will not be important enough for the final star to burn hydrogen. Their formation mechanism is not well constrained, we must find and characterize a first candidate pre-brown dwarf. Oph B-11 was detected along a nearby shock, we characterize chemically. Moreover, higher resolution studies with ALMA show a structured molecular environment and help us constrain the mechanism of formation of this kind of objects. These observations show a series of shocks in different tracers, spatially coincident with the detected position of the pre-brown dwarf, in favour of the gravo- turbulent scenario for the formation of brown dwarfs. I will discuss the legacy of Herschel in the Ophiuchus region in the filament paradigm of star-formation, and the future of these studies with the advent of new instruments, like NIKA2 and its polarimetry facility.
 
Vendredi 21 décembre 2018, 14h00
Salle de l'atelier, Paris
Astrochemistry in star forming regions : new modeling approaches
Emeric BRON
IRAM/LERMA
résumé :
Star-forming regions present rich infrared and millimeter spectra emitted by the gas exposed to the feedback of young stars. This emission is increasingly used to study the star formation cycle in other galaxies, but results from a complex interplay of physical and chemical processes : chemistry in the gas and on grain surfaces, (de)excitation processes of the atoms and molecules, heating and cooling balance,... Its understanding thus requires detailed astrochemical models that include the couplings between these processes. In this talk, I will present several examples where new modeling approaches of specific processes and their couplings proved crucial to solve persistent observational riddles : from the driving role of UV irradiation in the dynamics of photodissociation regions (PDR) to the efficient reformation of molecular hydrogen in these regions.
 
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